a geo-referenced census frame of dwellings for the 2011 census...

Innovative Methodologies for Censuses in the New Millennium, a satellite meeting of the 56th

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the ISI, 31 August – 2 September 2007, Southampton, UK

Sharthi Laldaparsad, Republic of South Africa, Statistics South Africa, Geography Division page 1 of 8

A Geo-referenced Census Frame of Dwellings for the 2011

Census of the Republic of South Africa

Sharthi Laldaparsad

Statistics South Africa, Geography Division

Abstract For the first time in the South African census taking history, Statistics South Africa (Stats

SA) is recording and using the position of every dwelling in the country in its preparation

towards Census 2011. Such a frame of dwellings is not available in the country, and there

is no address register, with many rural dwellings not ever having been assigned an

address. The statistics office has prioritised the creation of a geo-referenced dwelling

frame in preparation for and monitoring of operations, to ensure that all dwellings in the

country are covered during enumeration. The longer-term vision is to establish a

continuously maintained geo-referenced register of dwellings, establishments and

buildings.

The reliance on partnerships with other national government departments and agencies,

as well as local authorities, is key to the initiative. The development and maintenance of a

dwelling frame is of great interest to various government role players, as an enabler of

physical service delivery, emergency response services, billing systems, property

valuation rolls and financial services to citizens. In areas where addresses are available,

such as large urban areas, the dwelling frame will integrate, standardise and continuously

keep updated such a frame by partnering with local municipalities as data custodians.

The methodology to geo-reference dwellings makes use of high resolution aerial

photography and satellite imagery. This imagery is acquired through cost-sharing

arrangements with other government departments. An office exercise takes place to point

capture each dwelling from the photos using a Geographical Information System (GIS),

followed by a field exercise to verify points and capture new points using Global

Positioning System (GPS) technology, as well as capturing of about 18 attributes on each

built structure. This information is then integrated into the organisation’s spatial database

and updated on the website.

The attributes of each dwelling which are captured cover elements of what would be

included in a housing census, and the possible contribution of the dwelling frame to the

collection of information usually undertaken in a census of housing is being explored.

Since the characteristics and locations of establishments and other buildings (e.g. schools,

clinics, etc.) are also recorded during the capturing of dwelling units, the frame can be

explored as a source for other statistical collections, such as information on informal

businesses, as well as in the compilation of building statistics.


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Background In our strategy to ensure complete coverage for the 2011 Census of Population and

Housing for South Africa and in our attempts to minimise census undercount, right from

the beginning of the census process, from the foundation phase of a census, that is, the

delineation of the country into census enumeration areas and easily understandable

cartography that enables clear boundary identification and mobility throughout the

country, Stats SA has embarked on the development of a Geo-referenced Dwelling

Frame.

The objectives of the Geo-referenced Dwelling Frame is to identity or locate and describe

all structures on the ground with an exact coordinate and supporting descriptive attributes

about the structure. The project includes the continuous maintenance of such a frame that

can be used for subsequent censuses and surveys.

The Geo-referenced Dwelling Frame started with the main focus on allocating addresses

to about 50% of the country’s residents that have no addresses - mainly in the former

homelands of South Africa. (As shown in the picture below the dwelling received

numbers from each of the different service providers, even Stats SA during the censuses

spray-painted numbers on the wall.)

The project was piloted in 2002 in the village of Botseleni in the province of Limpopo

where dwellings were geo-referenced and addresses were for the first time displayed on

homesteads. The project is gaining momentum and the target is to complete the entire

country by October 2009, in time for the 2011 Census Pilot.


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Methodology The project is divided into two parts, namely formal (areas where formal addresses exist,

linked to formal cadastre and property title deeds); and informal (areas where no

addresses exist, nor formal cadastre or title deeds).

For formal areas, address databases from local municipalities, cities, large towns and

metropolitan councils are received and compared with the 2001 Census dwelling unit

count and latest aerial photography. So far there are 2 050 956 dwellings from all six

metropolitan councils. We intend setting up memorandums of understandings (MoUs)

with local municipalities, cities, towns and metropolitan councils for the continued

maintenance of this data. The picture below shows a typical formal area, with aerial

photography, cadastre and dwelling points, which in this case has formal addresses linked

to street names and suburbs.

For informal areas in the country and areas with no information, aerial or satellite

photography is acquired, an office exercise to put points on each dwelling takes place,

then fieldworkers go into the areas to verify the point and collect the attribute data. A

digital photograph of the dwelling is also taken. (As shown in the pictures on the next

page.) Stats SA further conducts a 100% office quality assurance and a 3% field sample

quality assurance on the data.


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How census benefits

Updating and correcting the ‘place name’ database

During Census 1996 Stats SA developed a place name database. This is a database of

community names and its geographic extent (namely suburbs, towns, cities, villages,

etc.).The database was updated using limited administrative data and photography for

Census 2001. Information from the Geo-referenced Dwelling Frame now enables us to

update the place names database further. The picture below shows the different villages

as captured for each point on the Dwelling Frame. In this way the census output

geography for small areas is updated and corrected, reflecting a more realistic picture of

the situation on the ground.

Demarcation of Enumeration Areas

The delineation of enumeration areas (EAs) is made simpler. EAs will be split or

aggregated. In certain cases, portions of EAs will be dissolved or added to EAs according

to an EA size criteria based on the amount of dwellings.


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Other areas of use for the census:

• A stable frame of dwellings will be provided as lists for the enumeration phase. If EA boundaries are unclear (e.g. cutting through houses), the fieldworker refers to the list.

This limits the risk raised during previous censuses on poor EA boundaries that don’t

follow physical features.

• Monitoring of census enumeration per dwelling and ensuring as a minimum a questionnaire is returned for each dwelling point i.e. monitoring non-response per

dwelling and targeting dwellings for re-visits. This enables spatial monitoring,

tracking of progress and targeted remedial actions.

• Reconciliation can be done at the end to determine if all dwellings have been accounted for. Through its geographic identification duplicate data and missed data

can be identified.

• Internet options for completion of census questionnaires online can be built more confidently linking data directly to its geographic location.

• Knowing the exact location of each dwelling from which information is collected enables us to define areas for which aggregates are provided independently from the

collection unit (i.e. EAs).

• The rationalisation of the country’s main geographical areas (i.e. provinces, district councils, municipalities) can be done more correctly at a dwelling level.

• A continuously maintained Dwelling Frame can be used to estimate statistically the population of the country, this is especially needed since South Africa has moved

only recently to 10 yearly population censuses and more frequent data is still

required.

• The Dwelling Frame could substitute the Housing component of the Census of Population and Housing thus resulting in a shorter more focused population

questionnaire, which in most cases leads to better quality data.


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How statistics in general benefits Our vision is that the Dwelling Frame becomes the frame for all household based

censuses and surveys. By having an updated dwelling frame more accurate samples for

surveys can be drawn and improved data collection is envisaged.

Changes to the country’s official political boundaries puts great stress on census and

survey data, to continuously keep the both in synch and back tracking of time series data

for comparison purposes. Having exact dwelling locations, data can be provided with

greater accuracy for frequently changing political geographies.

The Dwelling Frame provides characteristics and locations of other structures (see table

below an example for one municipality). Information on the number and location of other

structures is beneficial for statistics related to education, health, policing, businesses, etc.

and improved service delivery, which goes beyond the scope of its planned use by us.

MNQUMA (EC122)

FEATURE USE Traditional

Urban

Formal

Urban

Informal

Rural

Formal TOTAL

Bank 0 4 0 0 4

Bottle Store 10 6 0 0 16

Business 62 209 10 1 282

Church / Place of Worship 386 40 15 1 442

Day Clinic 22 6 0 0 28

Demolished Structure 3,008 59 59 23 3,149

Dwelling Unit 51,548 6,520 3,400 293 61,761

Factory 0 37 1 0 38

Filling Station 3 7 0 0 10

Garage 1 3 0 0 4

Guest House / Lodge 1 6 0 0 7

Market 1 0 0 0 1

New Dwelling Under

Construction 1,993 347 87 22 2,449

Offices 18 37 6 2 63

Other 152 29 7 15 203

Sports, Oval, Stadium 1 4 0 0 5

Park 0 1 0 0 1

Police Station 2 5 0 0 7

Post Office 9 5 0 0 14

Holiday Home 58 47 0 0 105

Residential Hotel 1 9 0 0 10

School 472 52 5 5 534

Convent/ Monastery/

Religious Retreat 1 0 0 0 1

Old Age Homes 0 1 0 0 1

Hospital/ Frail Care

Centre 1 2 0 0 3

Initiation School 63 0 0 0 63

Prison/ Correctional 0 2 0 0 2


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Institution/ Police Cells

Boarding School Hostel 1 0 0 0 1

Student's Residence 1 40 0 9 50

Workers Hostel 28 28 9 0 65

Shop 406 29 6 0 441

Storage Room 26 1 1 0 28

Vacant Dwelling 6,432 208 509 64 7,213

Vacant Stand 0 192 0 0 192

TOTAL 64,707 7,936 4,115 435 77,193

Conclusion

The Dwelling Frame has enormous possibilities to improve and maybe fundamentally

change the conventional census and survey methodologies used by a statistical agency.

Register-based information from the Business Register, Population Register and the

Dwelling Frame (National Address Register) are the pillars and the future direction for

statistics. In addition the National Address Register gives the other two a sense of

location.

Through the Dwelling Frame unaddressed communities are identified and addressed.

Having an address is close to the hearts of the people of our country, it’s certainly seen as

a community driven project by engaging the local structures and community members,

contributing to the growth of the second economy in South Africa.

Its continued maintenance is important since its relevance goes beyond that for only

statistical purposes, to that of common infrastructural framework information for nation

building and inter-departmental support is crucial.

Acknowledgements

I would like to acknowledge the contributions made by all pioneers and current staff

members of the Address Project and Dwelling Frame Project from both within and

outside Stats SA.

a geo-referenced census frame of dwellings for the 2011 census...

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